The present invention relates to a rotary displacement piling equipment.
More precisely, the object of the invention is an equipment to bore a cylindrical hole into the soil, said hole being later fulfilled with concrete or concrete and reinforcement element to complete the pile.
The invention is especially well adapted to the realization of bored piles within contaminated soil. However, the present invention is not limited to this situation.
Rotary displacement piles have been constructed by various methods for more than 20 years but have not been widely used. They are, however, now becoming more popular because of rising spoil disposal costs and increasing difficulty in disposing of contaminated soil.
The system developed by the Fundex company uses a soil displacement cone which is attached to the bottom of a steel casing and screwed into the ground. The cone is left in the ground when the reinforcement and concrete are placed inside the casing to form the pile, which makes the pile expensive. The casing can be left in the ground to protect the concrete if necessary, or can be extracted after the concrete has been placed.
The systems of the Atlas and Omega companies use soil displacement bits which are rotated into the ground without casing to support the soil behind the bit or protect the concrete in the pile, therefore the range of soils in which they can be used is limited.
The object of the present invention is to provide an equipment for boring holes in the soil in view of making a bored pile which is compatible with a contaminated soil and which allows the consolidation of the soil about the hole to enhance the bearing capacity of the bored pile.
To achieve this object, according to the present invention, the rotary displacement piling equipment comprises:
a rotary displacement bit;
rod means having an upper end and a lower end connected to said bit;
casing means surrounding said driving rod means to be forced down into the soil;
a casing adapter having a lower end provided with a cylindrical collar for co-operating with the upper part of said casing means for entering said casing means with respect to said driving rod means and with an horizontal thrust face for applying a thrust at the upper end of said casing means, and an upper end, said driving means passing through said casing adapter;
a rotary drive box co-operating with said driving rod means for rotating said driving rod means, said rotary drive box being provided with connecting means to be connected to the upper end of said casing adapter, whereby said casing adapter is rotated by said rotary drive box; and
vertical supporting and guiding means for supporting and vertically guiding said rotary drive box.
It is understood that the displacement bit is not connected with the casing. Consequently, the bit can be withdrawn from the hole when the hole is completed and the casing can be left in the ground to protect the concrete of the pile.
Moreover, the soil is displaced laterally by the bit to bore the hole and no significant amount of soil penetrates into the casing above the bit. As a result, when the soil is contaminated, no polluted or contaminated material is to be stored and treated. Additionally, environmental problems are avoided.
According to a preferred embodiment of the invention, the rotary displacement bit comprises:
a spiral lower portion for laterally displacing the soil when said bit is rotated; and
an upper cylindrical portion having a diameter slightly smaller than the inner diameter of said casing means; and
connecting means for fixing said bit at the lower end of said driving rod means.
According to a still preferred embodiment, the casing adapter includes:
a side wall consisting of an upper section and a lower section, said upper and lower sections being connected by mechanical joint means, and said equipment further comprises an extension piece to be inserted between said upper and lower section of said side wall whereby the distance the lower end of the rotary displacement bit projects ahead the toe of the casing means can be adjusted.
Preferably, the casing adapter further comprises means for producing fluid jets directed to flow within said casing adapter and said casing means.
It is understood that, due to the fluid jets produced within the casing, the dust in the casing is caught. This feature is of particular interest when the soil is contaminated.
According to a preferred embodiment of the invention, the casing is rotated by the casing adapter.
Other features and advantages of the present invention will appear better on reading the following description of several embodiments of the invention given by way of non limiting examples.